1. Field of the Invention
The present invention relates to a sheet processing apparatus and a sheet processing method.
2. Description of the Related Art
Conventionally, a sheet processing apparatus connected to an image forming apparatus has the function of folding sheets output from the image forming apparatus in a Z shape as one of their functions. Further, the image forming apparatus has the function of reading a document bundle including mixed documents of different sizes by a scanner and outputting sheets on which the read documents have been copied, mixing sheets in different sizes.
By employing these functions, when mixed documents of different sizes in the same grouping, e.g., documents mixing the A3 size (420 mm by 297 mm) and the A4 size (297 mm by 210 mm), both of which belong to the same grouping, are printed, sheets of the A3 size can be Z-folded into sheets of the A4 size.
As an example of a technique for producing a sheet bundle using a folding function when sheets of different sheet sizes are mixed, a reference sheet is determined to be a standard of length and sheets longer than the reference sheet are subjected to Z-folding or double-folding to conform to a reference sheet length (see Japanese Patent Application Laid-Open No. 2003-160274).
In the above-mentioned conventional technique, however, the sheets are folded to have a reference sheet length. Therefore, the sheets having folding widths other than the reference sheet length cannot be included in the sheet bundle.